alum

Evidence of Dying

Rogers found alizarin, a dye produced from Madder root. The dye appeared to have been used to match new thread to older age-yellowed thread. In addition to the dye, Rogers found a gum substance (possibly gum Arabic) and alum, a common mordant used in medieval dying.

Ultraviolet and X-ray

Ultraviolet and x-ray photographs taken in 1978, before the carbon 14 dating samples were removed, indicated that there were chemical differences between the sample area and surrounding areas of the cloth. Moreover, Alan Adler, Emeritus Professor of Chemistry at Western Connecticut State University, had found a significant quantity of aluminum in yarn segments from the general area of the sample. It is not found on other samples from elsewhere on the shroud. Alum, an aluminum compound, the common mordant used with Madder root dye, was certainly an explanation.  Many wondered if the labs or church authorities had considered this evidence or were even aware of it when they changed (or adopted) the protocol.  The article in Inside the Vatican addressed this:

Asked whether he [Rogers] thought the authorities at Turin had been aware of such evidence as the 1978 photographs indicating that the corner of the Shroud from which they took the sample was unlike the rest of the cloth, Rogers responded that “it doesn't matter if they ignored it or were unaware of it.  Part of science is to assemble all the pertinent data.  They didn't even try.”